1.1. Field of the Invention
Electronic circuitry may be used to detect a luminescent response. In particular, one may use an optical application specific integrated circuit (OASIC), which combines analog signal conditioning, digital signal processing, and wireless transmission with a sensitive electro-optical detector. To achieve maximum sensitivity to the luminescent response of a bioreporter, an OASIC should be sensitive to light in the 400 nm to 700 nm (visible) range, should have low leakage current and low noise, and should have minimal sensitivity to changes in environmental factors such as temperature and humidity. Such devices may be manufactured via a standard complimentary-metal-oxide-semiconductor (CMOS) process on a single substrate.
1.2. Description of Related Art
A bioluminescent bioreporter is an organism that is genetically engineered to produce light when a particular substance is metabolized. For example, bioluminescent (lux) transcriptional gene fusions may be used to develop light emitting reporter bacterial strains that are able to sense the presence, bioavailability, and biodegradation of organic chemical pollutants such as naphthalene, toluene, and isopropylbenzene. In general, the lux reporter genes are placed under regulatory control of inducible degradative operons maintained in native or vector plasmids or integrated into the chromosome of the host strain.
Due to the widespread use of petroleum products and the current regulations requiring underground storage tanks to be upgraded, replaced or closed by December 1998, the number of petroleum-contaminated sites has abounded. Of particular concern for drinking water quality are the more water-soluble components, benzene, toluene, ethylbenzene and xylenes (BTEX). Natural attenuation which relies on in situ biodegradation of pollutants has received a large amount of attention especially for petroleum contaminants. While microorganisms capable of biodegradation of BTEX compounds are usually present at these sites, there is a need to know whether or not conditions are favorable for biodegradation to occur.
Bioluminescent reporters have been widely used for the real time non-destructive monitoring of gene expression. Heitzer et al. (1992) developed a quantitative assay for naphthalene bioavailability and biodegradation using a nah-lux reporter strain HK44 constructed by King et al. (1990) containing a lux transposon (Tn4431) insertion in nahG of the lower naphthalene degradation operon. The nah-lux reporter was expanded for use as an on-line optical biosensor for application in groundwater monitoring (Heitzer et al., 1994). Other lux fusions have been constructed for monitoring the expression of catabolic genes including those for degradation of isopropylbenzene (Selifonova et al., 1996) and toluene (Applegate et al., 1997).
In addition to catabolic gene fusions, a wide variety of genes and operons have been studied using lux fusions. Lux fusions have been constructed for monitoring heat shock genes expression, oxidative stress, presence of Hg(II) and alginate production. In all these cases, the lux fusions are plasmid-based and were constructed by placing the promoter of interest in front of the promoterless lux genes from Vibrio fischeri contained in pUCD615 (Rogowsky et al., 1987).
1.3. Deficiencies in the Prior Art
A need has arisen for a monolithic bioelectronic device that contains both a bioreporter and an OASIC, yet is very small, rugged, inexpensive, low power, and wireless. (A monolithic bioelectronic device is a device that contains biological and electrical components and that is constructed on a single substrate layer.) Such a bioluminescent bioreporter integrated circuit (BBIC) could detect substances such as pollutants, explosives, and heavy-metals residing in inhospitable areas such as groundwater, industrial process vessels, and battlefields. Applications for such a device include environmental pollutant detection, oil exploration, drug discovery, industrial process control, and hazardous chemical monitoring. The low cost of such sensors and the wide variety of deployment methods would allow a large number of them to be distributed over a wide area for very comprehensive coverage.